Health workers collect the body of a cholera victim in Petionville, Haiti, February 2011. The cholera outbreak in Haiti began in October 2010. Nearly 9,000 people have died. David Gilkey/NPR hide caption

itoggle caption David Gilkey/NPR

A new smartphone app gives a close-up view of a patient's eye. Screengrab from video by Peek Vision, produced in collaboration with Sony Mobile. hide caption

itoggle caption Screengrab from video by Peek Vision, produced in collaboration with Sony Mobile.

Patients receive treatment at the Chest Disease Hospital in Srinagar, India. The country has one of the highest rates of drug-resistant tuberculosis in the world, in part because antibiotics for the disease are poorly regulated by the government. Dar Yasin/AP hide caption

itoggle caption Dar Yasin/AP

A single Lassa fever virus particle, stained to show surface spikes — they're yellow — that help the virus infect its host cells. London School of Hygiene & Tropical Medicine hide caption

itoggle caption London School of Hygiene & Tropical Medicine

How can women in rural Nigeria get the care they need? That's what Columbia University graduate students in public health asked residents of Kadawawa, Nigeria. Courtesy of Alastair Ager and Alissa Pires hide caption

itoggle caption Courtesy of Alastair Ager and Alissa Pires

National Geographic writer and explorer Dan Buettner studies the world's longest-lived peoples and their lifestyles. Courtesy TEDxTC hide caption

itoggle caption Courtesy TEDxTC

Village chiefs, residents and government officials take to the streets to celebrate the Chienge district's accomplishment of bringing sanitation to every home. Mark Maseko/Courtesy of UNICEF Zambia hide caption

itoggle caption Mark Maseko/Courtesy of UNICEF Zambia

The Ebola outbreak "overwhelmed" the World Health Organization and made it clear the agency must change, WHO's director-general, Dr. Margaret Chan, said Monday in Geneva. Fabrice Coffrini /AFP/Getty Images hide caption

itoggle caption Fabrice Coffrini /AFP/Getty Images

Jenny Tenorio Gallegos, 35, in Lima, Peru, is being treated for drug-resistant TB. The treatment lasts two years and may rob her of her hearing. Jason Beaubien/NPR hide caption

itoggle caption Jason Beaubien/NPR

Families harvest poppy bulbs in the Badakhshan province of Afghanistan. To collect the opium, they score the bulbs and let the milky substance ooze out. The dried residue contains about 10 percent morphine. David Guttenfelder/AP/National Geographic hide caption

itoggle caption David Guttenfelder/AP/National Geographic

Researchers meet participants: (from left) investigator Jose Luis Roca; Dr. Ernesto Ortiz; study participants Rainer Leon and his mother, Rina Leon Chanbilla; and nurse Jennifer Rampas. Jason Beaubien/NPR hide caption

itoggle caption Jason Beaubien/NPR

Kids in Cape Town socialize as they walk to school. Children in South Africa often don't get to play outside by themselves because of the high rate of violent crimes in some areas. Henk Badenhorst/Getty Images hide caption

itoggle caption Henk Badenhorst/Getty Images

This aerial view shows the effects of gold mining on Peru's rain forest. Courtesy of Gregory Asner, Carnegie Institution for Science hide caption

itoggle caption Courtesy of Gregory Asner, Carnegie Institution for Science